FILTER ELEMENTS ONLY: Requires a 4” flange assembly, sold separately or as part of the starter kit Never wash another nasty filter sock again! Filter socks are arguably the worst part of aquarium maintenance and are the equivalent of cloth diapers that were used over 50 years ago. Why waste your time trying to clean a filter sock when you can simply replace it with a perfectly clean one every time? Reef Diaper disposable filter socks make this possible with low-cost replaceable filter elements. The top flange assembly is reused and only the filter element is replaced (flange assembly sold separately or as part of the starter kit). The simple design allows a new filter element to be installed in just seconds. The pleated element provides over 300 square inches of area and has the filter performance and capacity comparable to a 200 micron felt sock. The Reef Diaper is a simple, low cost alternative to bulky and complex roller filter systems. The reef diaper is perfect for both freshwater and saltwater aquariums. For maximum nutrient export, filter socks should be replaced twice a week.